1. Field of the Invention
This invention relates to the removal of deposits comprising heavy hydrocarbonaceous materials and finely divided inorganic solids from a tank using an alkyl polyglycoside surfactant composition.
2. Background of the Invention
Mixtures of oil, gas and water are frequently produced from oil fields. Processes for treating such mixtures to produce separate streams of oil, gas and water are well known. Typically the oil is separated and recovered as a product; the gas may be separated and recovered as a product; or, alternatively, the gas may be injected into a gas cap above an oil-bearing zone, into an oil-bearing zone or the like as recovered or as a miscible injectant which comprises the produced gas adjusted by the addition of nitrogen, carbon dioxide, hydrocarbons containing from one to about five carbon atoms and the like to adjust the specific gravity of the miscible injectant. The water may be recovered for injection or disposal by other means as known to those skilled in the art.
The separation is frequently accomplished in large settling (separator) tanks where the oil, gas and water are allowed to gravimetrically separate.
In many instances, the mixture of oil, gas and water is passed to central processing facilities for separation with the oil being recovered as a product and with the gas being either wholly or partially recovered as a product also. In some instances, the gas is redistributed to injection wells and injected; and, in some fields, the water is similarly recovered, passed to injection wells and injected into the formation.
It has been found, when such operations are conducted, especially when corrosion inhibitors are used in the lines leading from the wells to the central processing facility and the like, that, over a period of time, deposits of heavy hydrocarbonaceous materials and finely divided inorganic solids deposit on the inner surfaces of the lines and the separation tanks. These deposits typically comprise finely-divided inorganic particles such as produced solids which may include hydraulic fracturing proppant, formation sand, formation fines and precipitates of materials such as iron sulfide. These particles become coated with corrosion inhibitor or other hydrocarbonaceous materials and subsequently become coated with additional quantities of heavy hydrocarbonaceous material in the flowlines, settling tank and the like. These deposits are referred to herein as "schmoo". The schmoo is a slimy, oily substance which adheres to almost any surface with which it comes in contact, and is difficultly removed from any surface and particularly from the inner surfaces of flowlines, water injection lines into the formation, separation tanks and the like. The material is removable by pigging from flowlines which are of a sufficient size and configuration that pigs can be run through the lines. Such lines are routinely cleaned by pigging. Other lines, such as injection lines into wells, small diameter flowlines, the settling tank surfaces and formation surfaces cannot be reached by pigging operations and, accordingly, the schmoo accumulates in the settling tank on the inner surfaces of these pipe lines, on the surfaces of the well and the like. The separation tanks have typically been cleaned by removing the tank from service, draining the tank and physically cleaning the schmoo from the inner surfaces of the tank. This is a time-consuming, expensive and dangerous operation.
Accordingly, a continuing search has been directed to the development of a method for the removal of such deposits more efficiently and without the need to enter the tank to physically remove the deposits.